developerWorks has a new section I didn't know about, the Power Architecture Zone, dedicated to Power Architecture technology. You might ask, "What is Power Architecture technology?" It's a set of microporcessors produced by IBM that are the CPUs for Macintoshes and a lot of IBM eServer products.
There's also a blog on this topic, Power Architecture zone editor's notebook, by Nora Mikes, who just so happens to be the editor of the zone. She also has an article, "POWER to the people: A history of chipmaking at IBM"
So, if you want to learn more about the hardware used to run some of J2EE and WebSphere Application Server software, go check this out.